public object VisitUnaryExpr(UnaryExpr expr)
        {
            var right = Evaluate(expr.Right);

            switch (expr.Operator.Type)
            {
            case TokenType.Bang:
                return(!IsTruthy(right));

            case TokenType.Minus:
                CheckNumberOperand(expr.Operator, right);
                return(-(double)right);
            }

            // unreachable
            return(null);
        }
 public void VisitUnaryExpr(UnaryExpr expr)
 {
     Resolve(expr.Right);
 }
 public string VisitUnaryExpr(UnaryExpr expr)
 {
     return(Parenthesize(expr.Operator.Lexeme, expr.Right));
 }